Mechanical keyboards are commonly used to enter information in electronic devices. More recently, to save weight and reduce size, or maximize display area, many small electronic devices have switched to virtual keyboards displayed on a touch sensitive display, such as a capacitive display.
Capacitive touch sensors are used in many applications. For example, flat surfaces such as touch sensitive displays or touch pads are commonly used to provide user input to electronic devices such as computers, smartphones, and other electronic devices. A disadvantage of such devices is that, while they provide visual feedback of position, they fail to provide any tactile feedback to the user.
In an attempt to provide the benefits of a touch sensitive input for capture gestures and the accuracy and tactile feedback of a mechanical keyboard, a capacitive sensing surface has been used beneath a mechanical tactile keyboard to provide a combination of touch input and key input to electronic devices. A disadvantage of such an approach is that any spilled liquid or moisture on the keyboard will prevent operation of the capacitive sensing surface, and the presence of the keyboard prevents easy removal of the liquid. A further disadvantage of this approach is that the touch sensitive surface is separated from the user by the keycaps which reduces both sensitivity and accuracy of touch detection.
It would be useful, therefore, to provide an improved capacitive touch sensor and an alternative method to equip a mechanical keypad with touch functions and less sensitive to water residual. It is also promising to improve the horizontal resolution and sensitivity.